1. Field of the Invention
The present invention relates to a method and apparatus of wafer exposure, particularly to a method and apparatus of wafer exposure with correction feedback.
2. Description of the Prior Art
Photolithography is one of the most important technologies in semiconductor manufacturing. It seriously affects structures of MOS devices, such as patterns of layers and doped regions. Typically, the number of masks used in photolithography indicates the complexity of a manufacturing process.
The exposure of wafers is generally implemented in a way of xe2x80x9cStep and repeatxe2x80x9d to accomplish a high resolution of patterns transferred to the wafers, wherein the size of the pattern on the mask is equal to or larger than that of the pattern transferred on the wafer. That is to say, the pattern on the mask is projected and minified on one of portions or blocks of the wafer. This is repeatedly implemented for the blocks on the wafer one by one until the whole wafer is exposed.
Only the pattern of one of layers is transferred to the wafer after each block of the wafer is exposed. There are many patterns of layers and corresponding masks involved in one manufacturing process. Therefore, addition to piece alignment between the blocks of the wafer, overlay alignment between the patterns of the layers is essential to the photolithography processing step.
However, performance of one exposure system always slightly varies with time. For a precisely accurate exposure, the wafers processed by the exposure system must be measured to obtain corrections for parameters (recipe) used by the exposure system. The recipe will be corrected and used by the exposure system to process the following wafers.
Conventionally, recipe correction is implemented manually. Pilot wafers are processed by the exposure system and then measured to obtain the corrections with some approximate calculations. However, this is time-consuming and easy to result in mistakes, which is disadvantageous to the throughput of the manufacturing process.
Therefore, the object of the present invention is to provide a method and apparatus of wafer exposure with auto-correction to eliminate the disadvantages resulting from manual operations.
The present invention provides a method of wafer exposure with correction feedback. The method comprises the steps of providing a first and second wafer, using a first group of parameters to expose the first wafer to transfer a pattern of a first layer to the first wafer, using a second group of parameters to perform overlay alignment of the pattern of the first layer with a pattern of a second layer for the first wafer, performing measurement of the first wafer to obtain a first and second correction respectively for the first and second group of the parameters, correcting the first group of the parameters with the first correction and using the first group of the corrected parameters to expose the second wafer to transfer the pattern of the first layer to the second wafer, and correcting the second group of the parameters with the second correction and using the second group of the corrected parameters to perform overlay alignment of the pattern of the first layer with the pattern of the second layer for the second wafer.
The present invention further provides an apparatus of wafer exposure with correction feedback. The apparatus comprises an exposure system using a first and second group of parameters to expose a first wafer to transfer a pattern of a first layer to the first wafer and to perform overlay alignment of the pattern of the first layer with a pattern of a second layer for the first wafer, respectively, and using the first and second group of corrected parameters to expose a second wafer to transfer the pattern of the first layer to the second wafer and to perform overlay alignment of the pattern of the first layer with the pattern of the second layer for the second wafer, respectively, a measurement system performing measurement of the first wafer to obtain a first and second correction for the first and second group of the parameters respectively, and a processing device correcting the first and second group of the parameters with the first and second correction, and sending the first and second group of the corrected parameters to the exposure system.
Thus, the corrected recipes are obtained by calculations of the processing device and automatically sent back to the exposure system. This avoids the manual operations which result in the disadvantages of the conventional exposure system.